1. Field of the Invention
The present invention relates to a drill apparatus, and to a corresponding method and computer program, for use in making holes in printed circuit boards, steel plates, plastic plates, and other plate materials. More specifically, the present invention relates to optimizing the drilling of many holes along a predetermined line.
2. Description of Related Art
In processing printed circuit boards and other materials, a series of circular holes is often formed in such a way that their combination produces a long and narrow linear hole. For example, this method may be used to make a series of holes in a printed circuit board designed for placing a semiconductor device (chip) thereon. FIG. 1 shows this type or processing, wherein five round holes are formed successively as shown in (b) to thus form a linear long and narrow hole as shown in (a). When the holes are made from 1 to 5 successively in the case of FIG. 1, a hole on the left side is already drilled at the time of drilling of holes 2, 3, 4, and 5, so that the stress applied to the drill bit differs between the left and right sides, resulting in an increased probability of drill bit breakage. Since replacing a broken drill bit requires much more time than the time needed for horizontal movement of a drill bit, it is desirable to keep the possibility of drill bit breakage as low as possible. Thus, the drilling order must be determined so that the drill bit receives uniform stress at its left and right sides as much as possible. For example, drilling in the order of 1, 5, 3, 2 and 4 as shown in (d) and (e) in the example of FIG. 1 is considered satisfactory. Drilling in accordance with such a predefined order so that uniform stress is applied at the left and right sides is called "slot drilling".
Conventional slot drilling, however, has typically required a manual determination to establish a prescribed drilling order, based on past experience. This, in turn, has caused a bottleneck, due to increased work hours required for the design of the drilling steps.